Great Aunt Greta is Henry and Peter's very old great-aunt who thinks Henry is a girl called Henrietta and Peter a teenager. She sends Peter cool stuff, and Henry girly stuff. In the movie, after Ashton Primary has closed down, Great Aunt Greta is paying for Henry and Peter's new schools, as they are expensive. She is sending Peter to Brickhouse School and Henry to The Girl's School. The girls there tease Henry for being at a girl's school. With Margaret's help, the two escape The Girl's School. Great Aunt Greta was played by Prunella Scales